1. Field of the Invention
The present invention relates to an apparatus and method for manufacturing a centrifugal pump that mitigates the effects of upthrust. More specifically, the invention relates to a submersible centrifugal pump having one or more passages through one or more diffuser vanes to communicate pressure and thus reduce the effects of upthrust force.
2. Description of the Related Art
Centrifugal pumps can include a series of alternating impellers and diffusers. The impellers can rotate together by, for example, being connected to a common shaft. Fluid enters a base of each impeller and travels radially outward through a passage defined by vanes within the impeller. Centrifugal force, from the rotation of the impeller, accelerates the fluid through the impeller passages. The fluid exits the impeller and enters the diffuser.
Each diffuser is stationary relative to the adjacent impeller. The fluid moves through diffuser passages, which are passages defined by vanes within the diffuser. As the fluid moves through the diffuser, the fluid's velocity decreases as its pressure increases. The fluid exits the diffuser to enter into a subsequent impeller.
Upthrust and downthrust forces can act on each impeller during operation. Upthrust forces, being force acting in the direction of fluid flow, can occur from the pressure of the fluid below the impeller. Downthrust forces can occur from the head pressure of the fluid above the impeller. In some operating conditions, upthrust forces can exceed downthrust forces, thereby causing the impeller to move axially in a downstream direction. The operating conditions can be, for example, when little head pressure exists. Head pressure can be low when first starting the pump or at a maximum flow condition. It is desirable to reduce the upthrust forces during times when upthrust force exceeds downthrust force.